Certain data communication networks, such as those based on the well-known synchronous optical network (SONET) or synchronous digital hierarchy (SDH) standards, can be configured to utilize a technique known as virtual concatenation. The SONET standard is described in Bellcore standards document GR-253 and ANSI standards document T1.105, both of which are incorporated by reference herein. The SDH standard is described in ITU-T standards document G.707, which is incorporated by reference herein.
In general, virtual concatenation allows a given data communication channel, also referred to as a virtual concatenation (VC) data stream, to be split into several smaller streams, commonly referred to as VC member streams. The set of VC member streams associated with a given VC data stream is also referred to as a virtually concatenated group (VCG) or a VC group. Each of the VC member streams can travel along a different path from a source node to a destination node. As a result, the different member streams typically experience different delays in transit from the source node to the destination node. Upon arrival at the destination node, the individual member streams are recombined into the original VC stream. This splitting and recombining of data traffic is designed to be completely invisible to the transmitting or receiving end users, and allows for a particularly efficient utilization of network bandwidth.
However, this bandwidth efficiency is obtained at the price of increased algorithmic complexity. In particular, the recombining of the individual VC member streams at the destination node requires special care. For example, the destination node must account for the fact that these individual member streams are likely to have encountered different delays along their respective paths. Furthermore, these delays may not be fixed, due to slight variations in the SONET clocks in the various paths. A process known as differential delay compensation is used to realign the individual member streams.
Virtual concatenation in the SONET context is defined in greater detail in the ANSI T1.105-199x standards document, which is part of the above-cited T1.105 document.
Additional details regarding conventional aspects of virtual concatenation can be found in, for example, D. Cavendish et al., “New Transport Services for Next-Generation SONET/SDH Systems,” IEEE Communications Magazine, pp. 80-97, May 2002, which is incorporated by reference herein.
A significant problem with conventional virtual concatenation techniques as described in the foregoing documents is that the differential delay compensation process can in certain circumstances lead to undesirable overflow or underflow conditions in the data buffers used for differential delay compensation at the destination node. This can result in excessive errors in a corresponding network-based communication system.
It is therefore apparent that a need exists for improved delay compensation in virtual concatenation applications.